How Hunter Harrison Has Turned Around Canadian Pacific

CALGARY, Alberta—To win control of Canadian Pacific Railway Ltd., activist investor William Ackman pitched an aggressive plan to turn "the worst performing railroad in North America" into one of the best.

Two years later, Hunter Harrison, the railroad veteran Mr. Ackman hired as CEO, is close to delivering on that promise. Mr. Ackman's Pershing Square Capital Management LP has already tripled the value of its initial $1.07...